Most computer systems have a built in a network interface apparatus (or network interface adapter) so as to link with internet. In general, the network interface apparatus is not transmitting packet at any time, even it could be a long time without transmitting any packet. Therefore, the network interface apparatus may have some power consumption modes can be selected to achieve the purpose of power saving. For example, the network interface apparatus can be set into power saving mode to save power when operating at non-link status or no packet transmitted.
It is necessary that the network interface apparatus informs the upper level circuit (for example: operating system, basic input/output system or chipset) in the computer system when the network interface apparatus will be operated in power saving mode or has already operated in power saving mode, so that the system can proceed with off loading and rearranging the resource of the network interface apparatus.
For current technology, in order to inform the upper level circuit in the computer system, a General Purpose Input/Output (GPIO) pin is utilized by the network interface apparatus to communicate with the upper level circuit. However, through GPIO pin to perform communication not only the network interface apparatus need another pin but also the upper level circuit. Thus, this approach will waste chip area, and additional wiring on the printed circuit board (PCB) is unavoidable as well.